During the operation of internal combustion engines, including diesel engines, gases resulting from an explosion in the cylinders of the engine are expelled from the cylinder in an initial high pressure pulse or wave. It has been determined that the initial high pressure wave or pulse has a relatively long duration, and is followed by a series of alternating low and high pressure waves of shorter duration. A series of alternating high and low pressure waves is formed in the exhaust manifold each time an exhaust valve for any one of a plurality of engine cylinders is opened. During the high pressure pulses, combustion products or exhaust gases are expelled from the cylinders of the engine. These exhaust gases often contain appreciable amounts of unburned fuel. However, during the low pressure pulses, the pressure inside the exhaust manifold falls below atmospheric and a vacuum is created.
The quantity of unburned fuel in the exhaust gases which are introduced into the exhaust manifold during a high pressure pulse or wave can be substantially reduced by inducting air into the exhaust manifold during the low pressure pulse. The induced air promotes more complete fuel combustion in the manner of an afterburner. Such an air injector thus serves as a mechanical emission control device. Experience has even shown that the inducted or injected air actually helps clean up the carbon deposits in an internal combustion engine.
In other words, the oxygen induced or injected into the hot gases of the exhaust manifold produces a more complete burn of the unoxidized gasoline or diesel fuel in the exhaust manifold. The injection of fresh air, including oxygen, into the exhaust manifold produces a more complete burn and reaction of exhaust gases and fuel within the exhaust manifold itself. In a diesel engine, this produces a better burn of the sulfur contained in the diesel fuel oil and a reduction of particulates which are conventionally vented out the exhaust stack. In a gasoline engine, the injection of air at this point results in a substantial reduction of the carbon monoxide and unburned hydrocarbons found in the the exhaust emissions of an internal combustion engine.
A number of devices have been developed to use the principle described above. For example, U.S. Pat. No. 2,345,569 teaches an atmospheric air vent in the exhaust manifold adjacent the cylinders, which vent has a check valve without substantial inertia in the vent which valve is responsive to alternating vacuum and pressure within the manifold. The valve is a very thin, light metal plate that is not permitted to rotate about its axis. It has been found that a problem with many of these prior devices is that if the valve has its motion limited in some way, as here, that the valve may be subject to sticking in an open or closed or even intermediate position thereby voiding its effectiveness.
An air intake check valve connected to the exhaust system is described in U.S. Pat. No. 2,854,816. The check valve has a movable, dome-shaped valve element for opening and closing the valve in step and in phase with the negative and positive half-cycles of the sonic pressure wave in the exhaust system, so as to cause intake of air during the negative half-cycles and resulting reduction in the amplitude of the negative half-cycles, thereby superimposing on the sonic pressure wave a second harmonic, yielding a complex resultant wave characterized by peaked positive pressure half-cycles and flattened negative pressure half-cycles. The movable valve element is frequency responsive to the complex resultant wave to open and close during and by virture of the flattened negative pressure half-cycle and to remain closed during the peaked positive pressure half-cycle. Air charges admitted during the negative pressure half-cycles of the sonic wave react with unburned fuel in the exhaust system during and by virtue of the peaked positive pressure half-cycles of the sonic wave.
U.S. Pat. No. 3,253,401 to Carter Wells discusses an air injector for an internal combustion engine exhaust manifold consisting of a tube with threaded opposite ends in combination with a series of baffle plates disposed in spaced relation in the tube. Each of the baffle plates are in a plane extending substantially diametrically of the tube and each of the plates have an aperture disposed on a side of the axis of the tube opposite the aperture in an adjacent baffle plate. Each baffle plate is spaced from an adjacent baffle plate to provide an air turbulating space. The baffles are to rarefy the exhaust gases as they progress toward the more remote or outer end of the tube. The flutter valve of this device is spring biased closed.
An exhaust manifold afterburner having an elongated reed valve with relatively stationary ends is taught in U.S. Pat. No. 3,314,230. The air injection device of this patent has a body containing an air passage with an air discharge terminal adapted for connection to the exhaust manifold and an air inlet spaced from the terminal. A control mechanism including the valve is carried by the body to control air flow through the body passage to the exhaust manifold in response to exhaust pressure fluctuations communicable to the valve. The reed valve is carried at the downstream side of a seat in such overlying relation thereto to flex away from and toward the seat to control air flow therethrough in response to exhaust pressure fluctuations. The seat projects downstream within the body to pass air therethrough and the body passage extends at the outer side of the seat to receive air flowing laterally between the reed valve and the seat when the reed is flexed away from the seat. The body is also flanged to closely support opposite end portions of the reed valve transversely outwardly of the seat, and in such a manner that the reed valve is free to rotate about an axis defined by the passage during valve flexing. Although this reed valve can rotate about its axis, sticking of the valve against the seat and the flange may still occur, further frustrating the purpose of the device. Valve sticking to the seat and flange surfaces is most likely to occur after the engine is idle for some time and the deposits on the surfaces adhere to each other.
U.S. Pat. No. 3,844,260 mentions an exhaust gas recirculating mechanism for reducing the pollutants discharged from an internal combustion engine by regulating the flow of a portion of the exhaust gases from the exhaust manifold to the intake manifold by the use of a plate valve mechanism that meters the flow of exhaust gases and/or ambient air in response to atmospheric pressure, intake manifold pressure and exhaust manifold pressure. In one form, a single plate valve is provided in the exhaust gas recirculating valve, and in a second form, dual plate valves are used. Included with the ambient air and exhaust gas recirculating mechanism is a velocity nozzle for introducing the gases into the intake manifold and for helping to scavenge the PCV system's crank case emissions. This rather complicated system may give good results if functioning properly, but the use of two plate valves instead of one doubles the possibility that the plates will encounter sticking problems in prolonged operation.
An internal combustion engine having, in communication with the exhaust system at a position where changes in exhaust gas pressure occur during running of the engine a valve constructed and arranged so that when the pressure in the exhaust system is subatmospheric the valve takes up an open condition to admit air into the exhaust system is described in U.S. Pat. No. 3,913,322. Further, when the pressure in the exhaust system is super-atmospheric, the valve takes up an at least partially closed condition so that at least some of the air admitted to the exhaust system through the valve will be drawn back into the engine cylinders. The valve is a free-floating metal disc valve having a plurality of various sized holes therein, but which may still be subject to the sticking problems described earlier.
Finally, there is known the assembly for mounting on an exhaust manifold of an internal combustion engine to induct air into the exhaust manifold during the low pressure portion of the exhaust pulses of the engine discussed in U.S. Pat. No. 4,815,284. The assembly includes a stem section adapted to be connected to the exhaust manifold which includes a stem passage. A hollow cylindrical member is connected to the stem section to form a valve chamber which houses an improved valve arrangement. The valve arrangement includes a coiled spring which extends into the valve chamber, a valve seat, and a valve member disc disposed between the coiled spring and the valve seat. The disc is supported by the coiled spring which urges the disc against the valve seat for closing the valve in the absence of manifold pressure. During the negative pressure portions of the exhaust pulse waves, the disc is displaced away from the valve seat for opening the valve and inducting air into the manifold. During the positive pressure portions of the exhaust pulse waves, the disc is displaced toward and seats against the valve seat for closing the valve. The assembly further includes a pump mechanism extending over the valve chamber for pumping air into the opened valve during the negative pressure portions of the exhaust pulse waves. In one embodiment of this device, three valve members are used, which triples the conventional risk of sticking. Sticking is also aggravated by the spring biasing of this structure which increases the likelihood that the valve plates will adhere to their seats and to each other with the aid of deposits, instead of dropping away from the seats when the pressure is reduced.
It would thus be desirable for an air injector to be devised which eliminates or substantially reduces the possibility of the valve mechanism sticking in one position or the other during operation.